The present invention relates to the attachment of ballast box structures to mining shovel rotating frames and in particular relates to a method and apparatus for conserving deck space on the mining shovel and reducing working load on the pins coupling the ballast box to the rotating frame by pinning the feet of each gantry rear leg through a corresponding orifice in a ballast box projection in axial alignment with the pin holding the ballast box to the rotating frame projection and the longitudinal axis of a corresponding gantry rear leg.
Large mining machine shovels comprise a stationary lower frame coupled to a main rotating frame by a center journal and bearing roller circle. Because these machines weigh millions of pounds and because of the tremendous forces exerted by the shovel in the forward portion of the machine in digging materials, a ballast box weighing several hundred thousand pounds must be attached to the rear of the main rotating frame in order to balance the structure. Typical field installation of ballast box structure to the rotating frames of the shovel in the past have employed bolted or welded connections. Where there are a plurality of bolted connections, the orifices for the bolts require precision machining and obviously the more bolt connections that are required the more precision machining is required. In addition, the bolts which are used to form the connections must be accurately preloaded or torqued and, of course, the more bolts that are used in the connection the greater the time required to do the preloading or torquing of the bolts when mounting the ballast box structure to the rotating frame. It is necessary that this accurate preloading take place in order to avoid fatigue failure of the bolts.
In other cases where welded connections are used to attach the ballast box structure to the shovel rotating frame, the shovel not only loses its modular construction because of the permanent welding of the ballast box structure to the rotating frame but also welded connections are very time consuming to perform when there is a large number of welds to be made. In addition, the welds must be accurately formed since poor weld quality promotes fatigue cracking.
The main rotating frame also supports an inverted V-shaped gantry which has cables coupled from its outer end to the outer end of the shovel boom to which the dipper or shovel and its associated arm are attached. The inverted V-shaped gantry has forward and rear legs attached to eye projections on the rotating frame.
The present invention maintains the modular construction of the power shovel with respect to the ballast box structure, conserves deck space of the power shovel and reduces working load on the pins coupling the ballast box to the rotating frame by forming projections on the ballast box which attach to eye projections on the rotating frame previously used to attach the gantry rear legs and then pinning the rear legs of the gantry through a second orifice on the ballast box projections instead of the eye projections on the rotating frame.
Thus, it is an object of the present invention to removably attach the gantry rear legs to the ballast box attaching projections instead of to the rotating frame eye projection.
It is still another object of the present invention to rigidly attach first and second pairs of parallel plate projections on the ballast box having first and second spaced orifices therein, attaching the ballast box to the rotating frame by mounting a pin through a first orifice of each of the pairs of parallel plates and the eye of a corresponding rotating frame projection while attaching each gantry rear leg to the second orifice in corresponding ones of the parallel plate projections.
It is yet another object of the present invention to form the first and second spaced orifices in each of the ballast box pair of parallel plate projections such that the center of each of said first and second orifices lies on a line corresponding to the center of the longitudinal axis of said gantry rear leg.